Manufacture of artificial leather



Patented Apr. 25, 1933 UNITED STATES PATENT OFFICE enonena. mcnrmwannacn n.

HAMPSHIRE ASSIGNORSIO BROWN 00 CORPORATION OF MAINE VAN ABSDEL AND ROGER B. OF BE ELIN, NEW

MANY, OF BERLIN,"NEW EADSHIRE, A

muracrru'nn or Aiirincmr. LEATHER No Drawing.

' aqueous rubber dispersion such as latex,

whereupon the liquid rubber-carrying vehicle is'removed from'the foundation as by drying. If desired, the rubber-impregnated foundation may then be vulcanized to produce a product of the desired strength and rigidity. V

For many purposes, it has been found advantageous to use as the foundation, a fluffy web composed of loosely felted fibers, as such a web is of high porosityland may be readily impregnated with latex, for example, and then dried, and, if desired, vulcanized, to produce a product, which simulates many of the desirable characteristics of natural leather. For instance, the rubber-impregnated product possesses sufiicient porosity and flexibility to be used as a raw material for the manufacture of inner soles where these characteristics are of prime importance. Because of the high porosity of the web used as a raw material, after the removal of the liquid rubber-carrying vehicle from the web, considerable of the initial porosity is evidently restored, so that when the -.rub-.

her-impregnated product contains even as high as 100% or more rubber, based on dry fiber, it is suflicientlyporous to be breathed through and to absorb considerable water. Consequently it is unsatisfactory for use in the manufacture of articles, such as midsoles and outsoles, as in such case it must be quite rigid and must resist absorption of and penetration-by water, under the action'of which it swells considerably and squeezes out under the pressure of the foot'to beyond its normal size, in which condition it sets permanently. If the waterproof qualities of the product are improved by increasing used in 1 Application filed September 17,1929. Serial No. 393,310.

its rubber content, it acquires a distinctly rubbery feel and-has even greater flexibility.

I have found that for some articles, such as mid-soles and out-sole's, it is highly adyantageous to impregnate a porous rubberimpregnated web such as described, with resinous materials preferably the non-brittle, artificial resins such as used in the socalled bakelite varnishes. I have found that when a dried, latex-impregnatcd web of porous structure is impregnated with a solution of bakelite varnish and is then dried and, if, desired, cured, the finished product possesses greater rigidity under pressure even while wet, and is more resistant to swelling by the action of water, being comparable to natural leather in these respects. The finished product is also, of much hlgher' tensile strength.

e various types of foundations may be producing the product of the present mvent1on,it is preferable to employ a flufl'y web co posed of loosely interfelted cellulose fibers and possessing high porosity. A web of unusually high porosity may be pro duced by using a substantially unbeaten wood fiber of high alpha cellulose content, say 94% or greater, as a raw material, and forming such fiber into a web machine designed to effect dewatering and drying'of the web without the application of the heavy pressures used making practice. While other fibers in substantially unbeaten condition, such as sulphite, kraft, or soda'pul ,may be employed, a substantially unbeaten wood fiber of high alpha cellulose content is preferred because For instance, we

on a paper-making in ordinary paperit is more highly absorptive than the usual may be passed through a bath of rubber-carrying vehicle, such as an ammonia-preserved latex of a solids content, of say, about 16%,

at-which content immersion for about one half minute to one minute effects a thorough impregnation of the web, whereupon the web may besqueezed\ until its rubber solids oontent is about 110%, based on the weight of term metal, preferably zincoxide, as described in application Serial No. 369,267, filed June 7, 1929 by Roger B. Hill, or with alkaline earth metal hydroxides, preferably slaked lime, as described in application Serial No. 373.055, filed June 22 192% by Roger B.

Hill. When slaked lime is the compound addedto the latex to overcome migration tendencies during drying, protective colloids such as soluble soaps or caseinates which are capable of being precipitated by lime as insoluble calcium soaps or casein-ates, are preferably added to the latex prior to the addition of the sla-ked lime in order to overcome coagulating tendencies. Such treatment of the latex prior to its use for the impregnation of the webmakes possible the production of a dried rubber-impregnated web of uniformity in. respect of rubber distribution therethrough, as troublesome non-rubber constituents of the latex, namely, the proteins and the resins are converted to an insoluble, inert condition. Apparently, setting or coegula tion of the rubber by drying is so retarded by the proteins and resins which exist respectively in an ammonia-preserved latex as water-soluble proteinates and alkali resin ates, that there is a tendency for rubber particles to migrate to the surface of the impregnated product, where evaporation of water is taking place. The tendency for m1- gration of rubber particles is especially pronounced in the case of highly porous webs of cellulose fiber of the. type described, evidently because of the high capillary action taking place during drying to cause. such migration.

If desired, a vulcanized latex may be used so that when the latex-impregnated web is subsequently dried, the rubber will be coagu lated in the web in vulcanized condition. Or

artificial aqueous dispersions oi crude or reclaimed rubber may be used in lieu of natural latex. Suitable rubber-compoundingmterials, vulcanizingagents, an a or natural rubber dispersion so that the dried rubber-impregnated web may be vulcanized, if desired.

After the porous web has been impregrmted as hereinbefore described, it is dried. The

dried product is porous but the fibers are strongly bonded together by the rubber coagulated the-rein by drying, so that the initially weak web has'undergone a great iiicrease in tensile strength and tear resistonce. If not already vulcanized by the use of vulcanized latex, the product may be vulcanized under heat or by treatment with sulphur chloride fumes or with a solution of sulphur chloride. ina suitable solvent, as decceler'atm's. of I vulcanization, may be added to the artificial scribed in application Serial No. 392,480, filed September 13, 1929, by George A. Richter.

The porous rubber-impregnated web may then be passed through a solution of a suitable resinous material, preferably a. 10% solution ota bakelite varnish of about solids content in a suitable solvent or thinner. At this concentration, the bakelite solution is thin and easy flowing so that upon immersionfor about one-halt minute to one minute, the web is thoroughly impregnated with the solution and contains about 20% bakelite solids based on the weight of dry fiber. The varnish-impregnated web may then be airdried, and when an air-drying bakelite varnish is-em-ployed, no heat treatment of the dried product is necessary. If an intermediate type of bakelite varnish is used, the

driedproduct should be heated or cured to render the bakelite varnish infusible and insoluble. The heat treatment or curing may be accomplished at a temperature and for aperiod ofitime depending upon the flexibility desired in the final product. For instance, cu-ri-ngmay be effected as on steam-heated drums, at say 135 6., for about 90 minutes, under which conditions a product eminently suitable for use in the manufacture of soles is produced.

We present herein a table giving certain important charsctemiatics possessed by a rubber-impregnated web containing 1.10% rubber based on the weight of dry fiber and a similar rubber-impregnated web additionally impregnated with about 20% bakelite solids based on the weight of dry fiber.

Rubber- Rubberv naked and TM ai 3mm impregnated web M simgth (lac. perm. iu.) wan--- 925 1950 Act08S-- 650 -1105 M (75) With.... 17. 2 O 4. 7 AcmaL B. 2 10. 2 Permanent set With... 9. 4 5. 6 I Across. 15. 6 8. 6 T- moisten:- With.-. 238 213 Across- 318 82 The various tests hereinbefore given were made. with and across the sheet, that is, in the direction of the paper machine and across the paper-machine. It is to be noted that impregnation of the rubber impregnated web with hakelite varnish effects a marked increase in the tensile strength of the product and a marked decrease in its stretch and in its so-called permanent set. The permanent set value is obtained by stretching the product and noting the rmanent increase in length after recovery IS permitted. The tear resistance of the bakelite-varnish impregnated product is lower than that ofa product impregnated with rubber alone, but this charaeteristic is of no particular moment where mos-me v the product is intended for such use as in the manufacture of shoe soles.

The original untreated web is preferably made comparatively thin so that its impregnation and drying may be easily efiected. Accordingly the impregnated sheet is usually of insuficient thickness for the manufacture of such products as mid-solesorout-soles, it being necessary to bond together two or more Sheets. The bonding together of the sheets dried. Ap srently the iuitiel moiste or.

wetting o the plies promotes penetration of the thick latex into the surface portion of the plies and results in a better interlocking of the plies after the latex is dried. Were the plies bonded together before impregnation with bekelite varnish, the membrane of rubber formed between the plies would interfere with penetration of the varnish throughout the plied product. p

By introducing a. resinous material into the pores of the web after they have been partially filled with. rubber, as hereinbefore described, apparently little combination 7 takes place between the resinous material and the rubber, each of these impregnating materials existing independently in the fin ishedproduct and importing desired chemoteristlcs thereto, as distinguished from the rubber compound produced when resinous materiel is incorporated into rubber on compounding rolls or in mixers.

The specific example hcreinbefore given.

deals with-the use of bskelite vernish es the resinous material, as this material has been found to give the best results. 7 Any one of 9..

large number of types of bekelitc varnishes may be employed depending upon the fiexibility desired in the final product. The proportions of rubber and resinous materiel presentin the finished product may very, but

when the product is intended for the manufacture of shoe soles, it should contain a com paratively large amount of rubber and a comparatively small amount of resinous material. Other changes and modifications might be made without departing from the spirit or scope of this invention as defined in the appended claims.

What we claim is:

1. Sheet material comprising a porous foundation oi fibrous material impregnated throughout with rubber and with non-brittle, resinous material of the nature of bakelite.

2. Sheet materi l ompris g a por us and with non-brittle, resinous material of the nature of bakelite.

5. A shoe sole comprising a. porous foundation of interfelted cellulose fiber containing about 100% of rubber and about 20% of nonbrittle, resinous 'material of the nature of bakclite based on the weight of dry fiber, uuiformly distributed thercthrough.

6. A process which comprises impregnate ing a. porous foundation 0 fibrous materiel with. rubber while preserving considerable of its porosity, and then impregnating said foundation with a. non-brittle, resinous ma.- terial of the nature of bckelite.

7. A process which comi'prises impregnat ingo porous foundation 0 iuterfclted cellulose fiber with a. rubber-carrying liquid vehiclc, removing said vehicle; impregnating with a. solution of non-brittle, resinous ma.- tcriel of the nature of bolielite, and removing the solvent. j

8. A. process which comprises impregnating a, porous foundation of iuterfelted cellulose fiber with an aqueous dispersion of rubber, drying scid foundation, impregnating with a solution of bclxelite vernisb, and removing tbe solvent.

9. A. process which comprises impregnatings porous foundation of interfeltcd cellulose fiber with on aqueous dispersion of rubbor, drying seid foundation, impregnating with a. solution of bekelite varnish, remov bug the solvent, sud cur-i at elevated tempereture.

10. A porous. rubberized sheet of interfeltcd cellulose fibers, the poresof' which contain a non-brittle, resinous material of the nu.- ture of bakelito.

11. A porous sheet of rubberized iuterfelted cellulose fibers, the pores of which contain bakelite varnish.

In testimony whereof we have signatures.

GEORGE A. RIGHTER. WALLACE B. VAN ARSDEL. ROGERB. 

